This description relates to damper control in space heating and cooling.
During the 1990s, the United States Department of Energy sponsored research on how to save energy in heating and cooling houses and other buildings. As shown in FIG. 1, one recommendation that has begun to be widely adopted is to super-insulate buildings, seal them tightly against air infiltration, and use a vent 10 from the outside world 12 to let in fresh air. The fresh air is needed to clear odors and humidity from the tightly sealed spaces 14 that are occupied within the buildings. The energy savings produced by such a system are so large that it is expected that, in the future, most new buildings will be super-insulated and tightly sealed.
As is typical of forced air heating or cooling systems, the heater or cooler 16, 18 (and a central fan 20) is turned on and off in response to a thermostat and controller 22 based on a comparison of a set point temperature and a current air temperature measured at a temperature sensor 24. The central fan 20 forces air from the heater or cooler through ducts 26 into the occupied spaces 14. Stale air is withdrawn from the spaces through return ducts 27 and returned to the intake side of the air handler. While the heater or cooler is running, the stale returned air is supplemented with fresh air that is drawn into the building through the vent 10. A damper 28 inside vent 10 is set in a fixed position to permit no more than a suitable amount of fresh air to be drawn in while the heater or cooler is running.
Even during intervals when the heater or cooler is not running, fresh air continues to be needed, and for this purpose, the central fan may be run from time to time during those intervals.
Heating and cooling systems are generally sized so that they run almost full-time during the coldest or warmest months. When a system that draws in fresh air from the outside world runs all the time, more air is drawn in than is needed for air exchange purposes, and energy is wasted in heating or cooling it. By motorizing the damper 28, it is possible to open and close the damper in cycles to reduce the amount of fresh air drawn into the building. In some systems, a user can specify the proportion of time that the damper is opened to permit fresh air to be drawn in. A replaceable filter 29 is included in the vent to filter the incoming air.
The cooler and/or heater are part of what is often called an air handler 32, which may also include a humidifier and/or a dehumidifier 34, and a variety of other equipment. A variety of configurations are used for air handlers, the equipment that is in them, and the equipment to which they are connected.
The air in the air handler can be heated and/or cooled in a variety of ways. A typical cooler includes the heat exchanger 18, a compressor 36 located outside the building, a delivery conduit 38 with a pump 40 to force coolant from the compressor to the exchanger and a return conduit 42 to carry used coolant back to the compressor. The pump is controlled by the controller 22.